The invention relates to an arrangement for measuring the temperature of an electronic circuit.
In the manufacture of semiconductor circuits, particularly monolithically integrated semiconductor circuits, a test, denoted as pre-measurement, is usually performed after finishing the conductor structures on the semiconductor body and before incorporating the semiconductor body in a housing, so as to reject defective circuits before they are incorporated in the housing. Moreover, a classification or specification of the semiconductor circuits based on their operating data can be performed with this pre-measurement. A condition for a correct pre-measurement is the knowledge of the instantaneous temperature of the semiconductor body, because many measuring values are temperature-dependent.
It is an object of the invention to provide an arrangement with which a measurement of the instantaneous temperature of the semiconductor body is possible in a simple, rapid and accurate manner.
According to the invention, this object is achieved by an arrangement for measuring the temperature of an electronic circuit, the arrangement comprising
a measuring element being in close thermal communication with the electronic circuit, which measuring element comprises a temperature-dependent component in each one of at least two current paths and whose current-voltage characteristic is dependent on the temperature in accordance with a different predetermined function in at least two of the current paths, which temperature-dependent components can each be impressed with a predetermined current for generating a voltage dependent on the temperature at each one of the temperature-dependent components, and
an evaluation circuit for forming an output voltage representing a measure of the temperature of the electronic circuit from the difference of the voltages at the temperature-dependent components.
By measuring the output voltage of the arrangement according to the invention, it is possible to measure the instantaneous temperature of the semiconductor body in a simple, rapid and accurate manner. The measured value of the temperature may be directly evaluated by means of an electronic signal processing operation, for example, in an apparatus for performing the pre-measurement.
Moreover, the arrangement according to the invention may also be used in the specifically defined operation of the electronic circuit for a continuous temperature observation. Measures for protecting the electronic circuit, for example, from overheating can then be taken in a very simple manner.
The temperature-dependent components are preferably formed with semiconductor diodes. These semiconductor diodes have a simple structure and can be provided in an electronic circuit without any additional manufacturing steps. Their temperature dependence is satisfactorily reproducible.
Particularly, the semiconductor diodes arranged in the different current paths are formed with different surfaces of their semiconductor junctions. This provides the easy possibility of manufacturing them in accordance with different predetermined functions of the temperature-dependent components without changing manufacturing parameters, for example, in the diffusion of the conductor structures of the semiconductor body of the electronic circuit.
In accordance with a further embodiment of the arrangement according to the invention, the temperature-dependent components are interconnected by way of a respective first one of their terminals, and their respective second terminals are connected to a device for impressing at least substantially identical currents. In accordance with the different temperature dependencies of the current voltage characteristics of the temperature-dependent components, different temperature-dependent voltages are generated at the temperature-dependent components, which voltage differences can be measured and evaluated easily and accurately.
Advantageously, the device for impressing at least substantially identical currents comprises a current mirror arrangement with which corresponding currents can be generated and supplied easily and accurately.
Advantageously, the interconnected first terminals of the temperature-dependent components are preferably coupled to a device for supplying a reference voltage. The measurement of the temperature-dependent voltages at the individual temperature-dependent components is performed with respect to this reference voltage. In particular, the reference voltage does not correspond to a ground potential provided by the electronic circuit at, for example, a ground conductor system in the electronic circuit, but the reference voltage is rather generated in a preferably separate temperature-stable manner. In accordance with an advantageous further embodiment of the invention, this can be achieved in that the device for supplying a reference voltage is formed with a bandgap reference from which the reference voltage is derived. By utilizing the reference voltage generated in a separate temperature-stable manner instead of the ground potential, inaccuracies in the temperature measurement, as may occur due to local fluctuations of the ground conductor system in the electronic circuit, are eliminated.
In a further embodiment of the invention, the evaluation circuit comprises
at least an inverter stage for inverting at least one of the temperature-dependent voltages at at least one of the temperature-dependent components,
at least a voltage combination stage for forming a voltage value which corresponds to the arithmetic mean value of at least one of the temperature-dependent voltages at at least one of the temperature-dependent components and at least one of the inverted temperature-dependent voltages at at least a further one of the temperature-dependent components, and
an output amplifier stage for amplifying and supplying the voltage value formed by the voltage combination stage as an output voltage representing a measure of the temperature of the electronic circuit.
This embodiment of the evaluation stage provides the possibility of determining the output voltage representing a measure of the temperature of the electronic circuit independently of indirect values such as the reference voltage and only by the dimensioning of the arrangement according to the invention.
In a further embodiment of the arrangement according to the invention described hereinbefore, in which the interconnected first terminals of the temperature-dependent components are coupled to a device for supplying a reference voltage, the evaluation circuit receives the same reference voltage for fixing its working point as the interconnected first terminals of the temperature-dependent components. This additionally enhances the accuracy of the temperature measurement. Moreover, the use of the internally generated reference voltage has the result that the components comprised by the arrangement according to the invention can be operated at optimal working points. As a result, the arrangement according to the invention operates to a very linear extent over a large temperature range.
In a further embodiment of the arrangement according to the invention described hereinbefore,
the electronic circuit, whose temperature is to be measured, is constituted as a monolithically integrated semiconductor circuit,
the measuring element and the evaluation circuit are combined with the electronic circuit constituted as a monolithically integrated semiconductor circuit on a semiconductor body, and
the electronic circuit constituted as a monolithically integrated semiconductor circuit comprises contacts for supplying and/or draining electric voltages and/or currents to and from the electronic circuit for supplying and draining power supply energy and/or signals, respectively, wherein
at least a first of these contacts is adapted to provide an output voltage of the evaluation circuit representing a measure of the temperature of the electronic circuit, and
at least a second contact provides the reference voltage applied to the temperature-dependent components at their interconnected first terminals as well as to the evaluation circuit for fixing its working point.
In this embodiment, the arrangement according to the invention is easily and directly usable for determining the temperature of the electronic circuit and for evaluating the measuring value of the temperature also outside the electronic circuit, for example, during a test of this circuit in a manufacturing process.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.